This is WEEKEND EDITION from NPR News. Good morning. I'm David Greene. Investigators from the United Nations have visited the site of a mass killing in Syria. Their initial report suggests that it was a attack on the Sunni Muslim village of Tremseh. They have been unable to confirm the death toll. Anti-government activists have called the attack on Tremseh a massacre, claiming more than 150 died. The Syrian government says it was an anti-terrorist operation and that no civilians were killed. NPR's Deborah Amos has been following the story and she joins us from Antakya, turkey. Deb, good morning.

DEBORAH AMOS, BYLINE: Good morning.

GREENE: So, Deb, let's try and sort this out. This, as I understand it, is the third recent mass killing in Syria. And each time they're just these completely opposite accounts from government officials and from anti-government activists. I mean, were U.N. observers able to get any clarity at all?

AMOS: Not really. The death count is still in dispute. I talked to a U.N. source last night who said that the bodies, both the wounded and the dead, have been removed before they got there. There are some facts that you can say are not in dispute. U.N. observers were outside the village on Thursday and they were eyewitnesses to heavy weapons. And they put that in their report. Now today, a spokesman for the foreign ministry came out and said they're wrong, that the Syrian government did not use heavy weapons. This was a military operation, they didn't use attack helicopters. So, now we have a third version of accounts of what happened in Tremseh.

GREENE: The government continues to use this term terrorists, and saying this was an anti-terrorist operation. I mean, have the U.N. observers been able to get a better sense of who exactly was being targeted by these pro-government forces?

AMOS: Here's what we don't know. Was this a deliberate slaughter - and that's what the activists say. Tremseh has long been an activist town - or was this a fight between rebels and government forces? That's what the U.N. can't answer. Now, I talked to some commanders here in Antakya and they confirm that the town was a rebel base. It's close to the city of Hama, and that city's been pounded by the Syrian army. So, a lot of these insurgents had fled to this little farming village. One defected army general here told me that more than 25 rebels were among the dead and a bunch of others fled 'cause they just ran out of bullets. This particular area is a sectarian fault line. There's been two other mass killings in this area, all the same pattern. These Sunni villages surrounded by Alawite communities.

GREENE: Alawites, of course, the religious sect that President Bashar al-Assad belongs to.

AMOS: Indeed. And this has become such a sectarian conflict. Many of the protesters, certainly many of the rebels are Sunni Muslims. The Alawite community supports the government, they share a religious sect with the president. And so it is such a combustible mixture.

GREENE: And, Deb, the U.N. monitors are going to be investigating these events again today. This is a U.N. mission that was suspended a few weeks ago because it was so dangerous. What has happened to make them feel safe and to be back at work?

AMOS: Well, that's a very good question because they were on the road near Tremseh on the day that the army began the offensive. I talked to a survivor in a Turkish hospital here and he said that he called them from a house where he was pinned down and told them to come, which means he had their number, which suggests that he is an activist or a rebel or both. Now, the mandate for these monitors was suspended after they said it was too dangerous for them to be out. But the government actually gave them permission to go in and investigate in Tremseh. And so it is very possible that the government feels they have a case in this town, certainly to their supporters, that this was a nest of terrorists, as they say, and they were coming in to fight them. But I think that we are not going to know. We didn't know in one other mass killing site. The U.N. was unable to be definitive on what happened here. I think that's likely going to happen again.

GREENE: All right. That's NPR's Deborah Amos who joined us from Antakya, Turkey. She's been following the ongoing violence in Syria. Thanks, Deb.